The role of macrophages in pulmonary hypertension: Pathogenesis and targeting

Novel Therapeutic Mechanisms and Strategies for Intracerebral Hemorrhage: Focusing on Exosomes

Intracerebral hemorrhage (ICH) is a primary, non-traumatic cerebral event associated with substantial mortality and disability. Despite advancements in understanding its etiology and refining diagnostic techniques, a validated treatment to significantly improve ICH prognosis remains elusive. Exosomes, a subtype of extracellular vesicles, encapsulate bioactive components, predominantly microRNAs (miRNAs), facilitating and regulating intercellular communication. Currently, exosomes have garnered considerable interests in clinical transformation for their nanostructure, minimal immunogenicity, low toxicity, inherent stability, and the ability to traverse the blood-brain barrier. A wealth of studies has demonstrated that exosomes can improve the prognosis of ICH through anti-apoptosis, neurogenesis, angiogenesis, anti-inflammation, immunomodulation, and autophagy, primarily via the transportation or overexpression of selected miRNAs. More importantly, exosomes can be easily customized with specific miRNAs or bioactive compounds to establish delivery systems, broadening their potential applications. This review focuses on the therapeutic potential of exosomes in ICH, reviewing the mechanisms of molecular biology mediated by certain miRNAs, discussing the benefits, challenges, and future prospects in ICH treatment. We hope comprehensive understanding of exosomes based on miRNAs will provide new insights into the treatment of ICH and guide the translation of exosome's research from laboratory to clinical practice.

Role of angiotensin converting enzyme in pathogenesis associated with immunity in cardiovascular diseases

Angiotensin converting enzyme (ACE) is not only a critical component in the renin-angiotensin system (RAS), but also suggested as an important mediator for immune response and activity, such as immune cell mobilization, metabolism, biogenesis of immunoregulatory molecules, etc. The chronic duration of cardiovascular diseases (CVD) has been increasingly considered to be triggered by uncontrolled pathologic immune reactions from myeloid cells and lymphocytes. Considering the potential anti-inflammatory effect of the traditional antihypertensive ACE inhibitor (ACEi), we attempt to elucidate whether ACE and its catalytically relevant substances as well as signaling pathways play a role in the immunity-related pathogenesis of common CVD, such as arterial hypertension, atherosclerosis and arrythmias. ACEi was also reported to benefit the prognoses of COVID-19-positive patients with CVD, and COVID-19 disease with preexisting CVD or subsequent cardiovascular damage is featured by a significant influx of immune cells and proinflammatory molecules, suggesting that ACE may also participate in COVID-19 induced cardiovascular injury, because COVID-19 disease basically triggers an overactive pathologic immune response. Hopefully, the ACE inhibition and manipulation of those associated bioactive signals could supplement the current medicinal management of various CVD and bring greater benefit to patients' cardiovascular health.

Omega-3 polyunsaturated fatty acids and pulmonary arterial hypertension: Insights and perspectives

Pulmonary arterial hypertension (PAH) is a rare and progressive disorder that affects the pulmonary vasculature. Although recent developments in pharmacotherapy have extended the life expectancy of PAH patients, their 5-year survival remains unacceptably low, underscoring the need for multitarget and more comprehensive approaches to managing the disease. This should incorporate not only medical, but also lifestyle interventions, including dietary changes and the use of nutraceutical support. Among these strategies, n-3 polyunsaturated fatty acids (n-3 PUFAs) are emerging as promising agents able to counteract the inflammatory component of PAH. In this narrative review, we aim at analysing the preclinical evidence for the impact of n-3 PUFAs on the pathogenesis and the course of PAH. Although evidence for the role of n-3 PUFAs deficiencies in the development and progression of PAH in humans is limited, preclinical studies suggest that these dietary components may influence several aspects of the pathobiology of PAH. Further clinical research should test the efficacy of n-3 PUFAs on top of approved clinical management. These studies will provide evidence on whether n-3 PUFAs can genuinely serve as a valuable tool to enhance the efficacy of pharmacotherapy in the treatment of PAH.

Inhalable Nitric Oxide Delivery Systems for Pulmonary Arterial Hypertension Treatment

Pulmonary arterial hypertension (PAH) is a severe medical condition characterized by elevated blood pressure in the pulmonary arteries. Nitric oxide (NO) is a gaseous signaling molecule with potent vasodilator effects; however, inhaled NO is limited in clinical practice because of the need for tracheal intubation and the toxicity of high NO concentrations. In this study, inhalable NO-releasing microspheres (NO inhalers) are fabricated to deliver nanomolar NO through a nebulizer. Two NO inhalers with distinct porous structures are prepared depending on the molecular weights of NO donors. It is confirmed that pore formation can be controlled by regulating the migration of water molecules from the external aqueous phase to the internal aqueous phase. Notably, open porous NO inhalers (OPNIs) can deliver NO deep into the lungs through a nebulizer. Furthermore, OPNIs exhibit vasodilatory and anti-inflammatory effects via sustained NO release. In conclusion, the findings suggest that OPNIs with highly porous structures have the potential to serve as tools for PAH treatment.

Novel insights and new therapeutic potentials for macrophages in pulmonary hypertension

Inflammation and immune processes underlie pulmonary hypertension progression. Two main different activated phenotypes of macrophages, classically activated M1 macrophages and alternatively activated M2 macrophages, are both involved in inflammatory processes related to pulmonary hypertension. Recent advances suggest that macrophages coordinate interactions among different proinflammatory and anti-inflammatory mediators, and other cellular components such as smooth muscle cells and fibroblasts. In this review, we summarize the current literature on the role of macrophages in the pathogenesis of pulmonary hypertension, including the origin of pulmonary macrophages and their response to triggers of pulmonary hypertension. We then discuss the interactions among macrophages, cytokines, and vascular adventitial fibroblasts in pulmonary hypertension, as well as the potential therapeutic benefits of macrophages in this disease. Identifying the critical role of macrophages in pulmonary hypertension will contribute to a comprehensive understanding of this pathophysiological abnormality, and may provide new perspectives for pulmonary hypertension management.

Forsythoside B Mitigates Monocrotaline-Induced Pulmonary Arterial Hypertension via Blocking the NF-κB Signaling Pathway to Attenuate Vascular Remodeling

Purpose

Pulmonary arterial hypertension (PAH) is a devastating disease with little effective treatment. The proliferation of pulmonary artery smooth muscle cells (PASMCs) induced by the nuclear factor-κB (NF-κB) signaling activation plays a pivotal role in the pathogenesis of PAH. Forsythoside B (FTS•B) possesses inhibitory effect on NF-κB signaling pathway. The present study aims to explore the effects and mechanisms of FTS•B in PAH.

Methods

Sprague-Dawley rats received monocrotaline (MCT) intraperitoneal injection to establish PAH model, and FTS•B was co-treated after MCT injection. Right ventricular hypertrophy and pulmonary artery pressure were measured by echocardiography and right heart catheterization, respectively. Histological alterations were detected by H&E staining and immunohistochemistry. FTS•B's role in PASMC proliferation and migration were evaluated by CCK-8 and wound healing assay. To investigate the underlying mechanisms, Western blotting, immunofluorescence staining and ELISA were conducted. The NF-κB activator PMA was used to investigate the role of NF-κB in FTS•B's protective effects against PAH.

Results

FTS•B markedly alleviated MCT-induced vascular remodeling and pulmonary artery pressure, and improved right ventricular hypertrophy and survival. FTS•B also reversed PDGF-BB-induced PASMC proliferation and migration, decreased PCNA and CyclinD1 expression in vitro. The elevated levels of IL-1β and IL-6 caused by MCT were decreased by FTS•B. Mechanistically, MCT-triggered phosphorylation of p65, IκBα, IKKα and IKKβ was blunted by FTS•B. FTS•B also reversed MCT-induced nuclear translocation of p65. However, all these protective effects were blocked by PMA-mediated NF-κB activation.

Conclusion

FTS•B effectively attenuates PAH by suppressing the NF-κB signaling pathway to attenuate vascular remodeling. FTS•B might be a promising drug candidate with clinical translational potential for the treatment of PAH.

Impact of reduced apolipoprotein A-I levels on pulmonary arterial hypertension

BACKGROUND

The significance of apolipoprotein A-I (ApoA-I) is the anti-inflammatory functional component of high-density lipoprotein, which needs to be further studied in relation to pulmonary arterial hypertension (PAH). This study aimed to identify the predictive value of ApoA-1 on the risk and prognosis of PAH, as well as the underlying anti-inflammatory mechanism.

METHODS

Proteomic analysis was conducted on lung tissue from 6 PAH patients and 4 lung donors. Prediction of risk and mortality risk factors associated with PAH in 343 patients used logistic analysis and Cox regression analysis, respectively. The protective function of ApoA-I was assessed in human pulmonary arterial endothelial cells (HPAEC), while its anti-inflammatory function was evaluated in THP-1 macrophages.

RESULTS

In the lung tissues of patients with PAH, 168 differentially expressed proteins were associated with lipid metabolism according to GO and KEGG enrichment analysis. A protein-protein interaction network identified ApoA-I as a key protein associated with PAH. Lower ApoA-I levels were independent risk factors for PAH and displayed a stronger predictive value for PAH mortality. Plasma interleukin 6 (IL-6) levels were positively correlated with risk stratification and was higher in PAH patients with lower ApoA-I levels. ApoA-I was downregulated in lung tissues of MCT-induced rats. ApoA-I could reduce IL-6-induced pro-proliferative and pro-migratory abilities of HPAEC and inhibit secretion of IL-6 from macrophages, which is compromised under hypoxic conditions.

CONCLUSION

Our study identified the significance of ApoA-I as a biomarker for predicting the survival outcome of PAH patients, which might relate to its altered anti-inflammatory properties.

Targeting EB3-IP3R3 Interface with Cognate Peptide Protects from Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a lung disease characterized by acute onset of noncardiogenic pulmonary edema, hypoxemia, and respiratory insufficiency. The current treatment for ARDS is mainly supportive in nature, providing a critical need for targeted pharmacological management. We addressed this medical problem by developing a pharmacological treatment for pulmonary vascular leakage, a culprit of alveolar damage and lung inflammation. Our novel therapeutic target is the microtubule accessory factor EB3 (end binding protein 3), which contributes to pulmonary vascular leakage by amplifying pathological calcium signaling in endothelial cells in response to inflammatory stimuli. EB3 interacts with IP3R3 (inositol 1,4,5-trisphosphate receptor 3) and orchestrates calcium release from endoplasmic reticulum stores. Here, we designed and tested the therapeutic benefits of a 14-aa peptide named CIPRI (cognate IP3 receptor inhibitor), which disrupted EB3-IP3R3 interaction in vitro and in lungs of mice challenged with endotoxin. Treatment with CIPRI or depletion of IP3R3 in lung microvascular endothelial monolayers mitigated calcium release from endoplasmic reticulum stores and prevented a disassembly of vascular endothelial cadherin junctions in response to the proinflammatory mediator α-thrombin. Furthermore, intravenous administration of CIPRI in mice mitigated inflammation-induced lung injury, blocked pulmonary microvascular leakage, prevented activation of NFAT (nuclear factor of activated T cells) signaling, and reduced production of proinflammatory cytokines in the lung tissue. CIPRI also improved survival of mice from endotoxemia and polymicrobial sepsis. Together, these data demonstrate that targeting EB3-IP3R3 interaction with a cognate peptide is a promising strategy to address hyperpermeability of microvessels in inflammatory lung diseases.

Perivascular inflammatory cells and their association with pulmonary arterial remodelling in dogs with pulmonary hypertension due to myxomatous mitral valve disease

Pulmonary hypertension (PH), an increase in pulmonary arterial pressure (PAP), may occur in dogs affected with myxomatous mitral valve disease (MMVD). Recent studies suggest that an accumulation of perivascular inflammatory cells may be involved with medial thickening which is a sign of the pulmonary artery remodelling in PH. The aim of this study was to characterise perivascular inflammatory cells in the surrounding pulmonary arteries of dogs with PH due to MMVD compared to MMVD dogs and healthy control dogs. Nineteen lung samples were collected from cadavers of small-breed dogs (control n = 5; MMVD n = 7; MMVD + PH n = 7). Toluidine blue stain and multiple IHC targeting α-SMA, vWF, CD20, CD68 and CD3 was performed to examine intimal and medial thickening, assess muscularisation of the small pulmonary arteries and characterise perivascular leucocytes. Medial thickening without intimal thickening of pulmonary arteries and muscularisation of normally non-muscularised small pulmonary arteries was observed in the MMVD and MMVD + PH groups compared with the control group. The perivascular numbers of B lymphocytes, T lymphocytes and macrophages was significantly increased in the MMVD + PH group compared with the MMVD and control groups. In contrast, the perivascular number of mast cells was significantly higher in the MMVD group compared with the MMVD + PH and control groups. This study suggested that pulmonary artery remodelling as medial thickening and muscularisation of the normally non-muscular small pulmonary arteries is accompanied by the accumulation of perivascular inflammatory cells.

Myeloid-derived suppressor cells and pulmonary hypertension

Pulmonary hypertension (PH) is a chronic pulmonary vascular disorder characterized by an increase in pulmonary vascular resistance and pulmonary arterial pressure. The detailed molecular mechanisms remain unclear. In recent decades, increasing evidence shows that altered immune microenvironment, comprised of immune cells, mesenchymal cells, extra-cellular matrix and signaling molecules, might induce the development of PH. Myeloid-derived suppressor cells (MDSCs) have been proposed over 30 years, and the functional importance of MDSCs in the immune system is appreciated recently. MDSCs are a heterogeneous group of cells that expand during cancer, chronic inflammation and infection, which have a remarkable ability to suppress T-cell responses and may exacerbate the development of diseases. Thus, targeting MDSCs has become a novel strategy to overcome immune evasion, especially in tumor immunotherapy. Nowadays, severe PH is accepted as a cancer-like disease, and MDSCs are closely related to the development and prognosis of PH. Here, we review the relationship between MDSCs and PH with respect to immune cells, cytokines, chemokines and metabolism, hoping that the key therapeutic targets of MDSCs can be identified in the treatment of PH, especially in severe PH.

Impact of l-citrulline on nitric oxide signaling and arginase activity in hypoxic human pulmonary artery endothelial cells

Impaired nitric oxide (NO) signaling contributes to the development of pulmonary hypertension (PH). The l-arginine precursor, l-citrulline, improves NO signaling and has therapeutic potential in PH. However, there is evidence that l-citrulline might increase arginase activity, which in turn, has been shown to contribute to PH. Our major purpose was to determine if l-citrulline increases arginase activity in hypoxic human pulmonary artery endothelial cells (PAECs). In addition, to avoid potential adverse effects from high dose l-citrulline monotherapy, we evaluated whether the effect on NO signaling is greater using co-treatment with l-citrulline and another agent that improves NO signaling, folic acid, than either alone. Arginase activity was measured in human PAECs cultured under hypoxic conditions in the presence of l-citrulline (0-1 mM). NO production and endothelial nitric oxide synthase (eNOS) coupling, as assessed by eNOS dimer-to-monomer ratios, were measured in PAECs treated with l-citrulline and/or folic acid (0.2 μM). Arginase activity increased in hypoxic PAECs treated with 1 mM but not with either 0.05 or 0.1 mM l-citrulline. Co-treatment with folic acid and 0.1 mM l-citrulline increased NO production and eNOS dimer-to-monomer ratios more than treatment with either alone. The potential to increase arginase activity suggests that there might be plasma l-citrulline concentrations that should not be exceeded when using l-citrulline to treat PH. Rather than progressively increasing the dose of l-citrulline as a monotherapy, co-therapy with l-citrulline and folic acid merits consideration, due to the possibility of achieving efficacy at lower doses and minimizing side effects.

PRDX6-mediated pulmonary artery endothelial cell ferroptosis contributes to monocrotaline-induced pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening cardiopulmonary disorder whose underlying pathogenesis is unknown. Our previous study showed that pulmonary endothelial cell (PAEC) ferroptosis is involved in the progression of PH by releasing High-mobility group box 1 (HMGB1) and activating Toll-like receptor 4/NOD-like receptor family pyrin domain containing 3 (TLR4/NLRP3) inflammasome signalling. The precise mechanisms that regulate ferroptosis in PH are unclear. This study aimed to investigate the effect of peroxiredoxin 6 (PRDX6) on PAEC ferroptosis in PH.

METHODS

A rat model of PH was established with monocrotaline (MCT), and the distribution and expression of PRDX6 in the pulmonary artery were examined. Lentiviral vectors carrying PRDX6 (LV-PRDX6) were transfected into PAECs and injected into MCT-induced PH rats. Cell viability, MDA levels, reactive oxygen species (ROS) levels, labile iron pool (LIP) levels and mitochondrial morphology were examined. Ferroptosis-related proteins (NADPH oxidase-4 (NOX4), glutathione peroxidase 4 (GPX4), and ferritin heavy chain 1(FTH1)), TLR4, NLRP3 inflammasome markers, HMGB1 and inflammatory cytokines were examined. Pulmonary vascular remodelling and right ventricular structure and function were measured.

RESULTS

PRDX6 was expressed in PAECs and was significantly decreased in PH. PRDX6 overexpression significantly inhibited ferroptosis in PAECs under PH conditions in vitro and in vivo, as indicated by increased cell viability, decreased MDA, ROS and LIP levels, inhibited mitochondrial damage, upregulated GPX4 and FTH1 expression, and downregulated NOX4 expression. PRDX6 overexpression attenuated pulmonary vascular remodelling and changes in right ventricle structure and function in MCT-induced PH rats. Moreover, PRDX6 overexpression prevented HMGB1 release by PAECs and decreased TLR4 and NLRP3 inflammasome expression and inflammatory cytokine release in macrophages, while RSL3, a specific activator of ferroptosis, reversed these effects.

CONCLUSIONS

Taken together, these findings indicate that PRDX6 regulates PAEC ferroptosis through the release of HMGB1 and activation of the TLR4/NLRP3 inflammasome signalling pathway, providing novel therapeutic targets for the treatment of PH.

STING mediates SU5416/hypoxia-induced pulmonary arterial hypertension in rats by regulating macrophage NLRP3 inflammasome activation

BACKGROUND

The NLRP3 inflammasome in macrophages is known to promote infection-related vascular growth, and NLRP3 inflammasome activation interacts with PAH. STING is a crucial inflammatory reaction link that can increase the overexpression of NLRP3. However, the expression and effect of STING in PAH have not been elucidated. We examined the expression and articulation of STING in PAH and researched its hidden mechanism.

METHODS

A SU5416 plus hypoxia (Su/Hy)-induced rat model of PAH was constructed to examine STING activation. Su/Hy induced PAH rats were given a prophylactic injection of STING the inhibitor C-176. After modeling, hemodynamic changes, right ventricular hypertrophy index, lung morphological features, inflammasome activation, and proinflammatory cytokine secretion levels were assessed. In addition, the STING agonist DMXAA or inhibitor C-176 was used to interfere with LPS-induced BMDMs, NLRP3 inflammasome activation and cytokine secretion were examined, and the effect on PASMCs was evaluated in a coculture system.

RESULTS

STING expression increased significantly in the lung tissue of Su/Hy-treated PAH rats compared with normoxia-treated rats. Moreover, STING inhibitors can alleviate the Su/Hy-induced increase in pulmonary artery pressure and restrain the activation of the NLRP3 inflammasome and proinflammatory cytokines. In vitro experiments confirmed that STING affected the expression of the NLRP3 inflammasome and the secretion of inflammatory cytokines in BMDMs and promoted the proliferation of PASMCs in the coculture system.

CONCLUSION

Our study shows that STING is activated in Su/Hy-induced PAH and boosts the actuation of the macrophage NLRP3 inflammasome to advance the inflammatory response and vascular proliferation in rats with Su/Hy-induced pulmonary hypertension.

Lasso algorithm and support vector machine strategy to screen pulmonary arterial hypertension gene diagnostic markers

BACKGROUND

This study employs machine learning strategy algorithms to screen the optimal gene signature of pulmonary arterial hypertension (PAH) under big data in the medical field.

METHODS

The public database Gene Expression Omnibus (GEO) was used to analyze datasets of 32 normal controls and 37 PAH disease samples. The enrichment analysis was performed after selecting the differentially expressed genes. Two machine learning methods, the least absolute shrinkage and selection operator (LASSO) and support vector machine (SVM), were used to identify the candidate genes. The external validation data set further tests the expression level and diagnostic value of candidate diagnostic genes. The diagnostic effectiveness was evaluated by obtaining the receiver operating characteristic curve (ROC). The convolution tool CIBERSORT was used to estimate the composition pattern of the immune cell subtypes and to perform correlation analysis based on the combined training dataset.

RESULTS

A total of 564 differentially expressed genes (DEGs) were screened in normal control and pulmonary hypertension samples. The enrichment analysis results were found to be closely related to cardiovascular diseases, inflammatory diseases, and immune-related pathways. The LASSO and SVM algorithms in machine learning used 5 × cross-validation to identify 9 and 7 characteristic genes. The two machine learning algorithms shared Caldesmon 1 (CALD1) and Solute Carrier Family 7 Member 11 (SLC7A11) as genetic signals highly correlated with PAH. The results showed that the area under ROC (AUC) of the specific characteristic diagnostic genes were CALD1 (AUC = 0.924) and SLC7A11 (AUC = 0.962), indicating that the two diagnostic genes have high diagnostic value.

CONCLUSION

CALD1 and SLC7A11 can be used as diagnostic markers of PAH to obtain new insights for the further study of the immune mechanism involved in PAH.

Hub Genes and Immune Cell Infiltration in Hypoxia-Induced Pulmonary Hypertension: Bioinformatics Analysis and In Vivo Validation

BACKGROUND

Hypoxia-induced pulmonary hypertension (HPH) represents a severe pulmonary disorder with high morbidity and mortality, which necessitates identifying the critical molecular mechanisms underlying HPH pathogenesis.

METHODS

The mRNA expression microarray GSE15197 (containing 8 pulmonary tissues from HPH and 13 normal controls) was downloaded from Gene Expression Omnibus (GEO). Gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) were executed by RStudio software. The Protein-Protein Interaction (PPI) network was visualized and established using Cytoscape, and the cytoHubba app from Cytoscape was used to pick out the hub modules. The infiltration of immune cells in HPH was analyzed using the CIBERSORTx. To confirm the potential hub genes, real-time quantitative reverse transcription PCR (qRT-PCR) was conducted using lung tissues of rat HPH models and controls.

RESULTS

A total of 852 upregulated and 547 downregulated genes were identified. The top terms in biological processes were apoptosis, proliferation, and regulation of the MAPK cascade, including ERK1/2. Cytoplasm, cytosol, and membrane were enriched in cellular component groups. Molecular functions mainly focus on protein binding, protein serine/threonine kinase activity and identical protein binding. KEGG analysis identified pathways in cancer, regulation of actin cytoskeleton and rap1 signaling pathway. There was significantly different immune cell infiltration between HPH and normal control samples. High proportions of the memory subsets of B cells and CD4 cells, Macrophages M2 subtype, and resting Dendritic cells were found in HPH samples, while high proportions of naive CD4 cells and resting mast cells were found in normal control samples. The qRT-PCR results showed that among the ten identified hub modules, FBXL3, FBXL13 and XCL1 mRNA levels were upregulated, while NEDD4L, NPFFR2 and EDN3 were downregulated in HPH rats compared with control rats.

CONCLUSION

Our study revealed the key genes and the involvement of immune cell infiltration in HPH, thus providing new insight into the pathogenesis of HPH and potential treatment targets for patients with HPH.

Targeting VEGF-A/VEGFR2 Y949 Signaling-Mediated Vascular Permeability Alleviates Hypoxic Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is associated with increased expression of VEGF-A (vascular endothelial growth factor A) and its receptor, VEGFR2 (vascular endothelial growth factor 2), but whether and how activation of VEGF-A signal participates in the pathogenesis of PH is unclear.

METHODS

VEGF-A/VEGFR2 signal activation and VEGFR2 Y949-dependent vascular leak were investigated in lung samples from patients with PH and mice exposed to hypoxia. To study their mechanistic roles in hypoxic PH, we examined right ventricle systolic pressure, right ventricular hypertrophy, and pulmonary vasculopathy in mutant mice carrying knock-in of phenylalanine that replaced the tyrosine at residual 949 of VEGFR2 (Vefgr2^Y949F) and mice with conditional endothelial deletion of Vegfr2 after chronic hypoxia exposure.

RESULTS

We show that PH leads to excessive pulmonary vascular leak in both patients and hypoxic mice, and this is because of an overactivated VEGF-A/VEGFR2 Y949 signaling axis. In the context of hypoxic PH, activation of Yes1 and c-Src and subsequent VE-cadherin phosphorylation in endothelial cells are involved in VEGFR2 Y949-induced vascular permeability. Abolishing VEGFR2 Y949 signaling by Vefgr2^Y949F point mutation was sufficient to prevent pulmonary vascular permeability and inhibit macrophage infiltration and Rac1 activation in smooth muscle cells under hypoxia exposure, thereby leading to alleviated PH manifestations, including muscularization of distal pulmonary arterioles, elevated right ventricle systolic pressure, and right ventricular hypertrophy. It is important that we found that VEGFR2 Y949 signaling in myeloid cells including macrophages was trivial and dispensable for hypoxia-induced vascular abnormalities and PH. In contrast with selective blockage of VEGFR2 Y949 signaling, disruption of the entire VEGFR2 signaling by conditional endothelial deletion of Vegfr2 promotes the development of PH.

CONCLUSIONS

Our results support the notion that VEGF-A/VEGFR2 Y949-dependent vascular permeability is an important determinant in the pathogenesis of PH and might serve as an attractive therapeutic target pathway for this disease.

Prevalence of Micronutrient Deficiencies and Relationship with Clinical and Patient-Related Outcomes in Pulmonary Hypertension Types I and IV

Background: Pulmonary hypertension (PH) is a rare progressive and lethal disease affecting pulmonary arteries and heart function. The disease may compromise the nutritional status of the patient, which impairs their physical performance. This study aimed to determine the prevalence of micronutrient deficiencies in pulmonary arterial hypertension (PAH) and chronic thrombo-embolic pulmonary hypertension (CTEPH) patients. Methods: Eighty-one blood samples from a prospective observational cohort study were analyzed for concentrations of micronutrients and inflammation-related factors. The samples consisted of newly diagnosed (treatment-naive) PAH and CTEPH patients and patients treated for 1.5 years according to ERS/ESC guidelines. Results: In the newly diagnosed group, 42% of PAH patients and 21% of CTEPH patients were iron deficient compared to 29% of PAH patients and 20% of CTEPH patients in the treatment group. Vitamin D deficiency occurred in 42% of the newly diagnosed PAH patients, 71% of the newly diagnosed CTEPH patients, 68% of the treated PAH patients, and 70% of the treated CTEPH patients. Iron levels correlated with the 6 min walking distance (6MWD). Conclusions: Iron and vitamin D deficiencies are highly prevalent in PAH and CTEPH patients, underlining the need for monitoring their status. Studies evaluating the effects of supplementation strategies for iron and vitamin D are necessary.

The Short-Chain Fatty Acid Butyrate Attenuates Pulmonary Vascular Remodeling and Inflammation in Hypoxia-Induced Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive cardiovascular disorder in which local vascular inflammation leads to increased pulmonary vascular remodeling and ultimately to right heart failure. The HDAC inhibitor butyrate, a product of microbial fermentation, is protective in inflammatory intestinal diseases, but little is known regarding its effect on extraintestinal diseases, such as PH. In this study, we tested the hypothesis that butyrate is protective in a Sprague-Dawley (SD) rat model of hypoxic PH. Treatment with butyrate (220 mg/kg intake) prevented hypoxia-induced right ventricular hypertrophy (RVH), hypoxia-induced increases in right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, and permeability. A reversal effect of butyrate (2200 mg/kg intake) was observed on elevated RVH. Butyrate treatment also increased the acetylation of histone H3, 25-34 kDa, and 34-50 kDa proteins in the total lung lysates of butyrate-treated animals. In addition, butyrate decreased hypoxia-induced accumulation of alveolar (mostly CD68+) and interstitial (CD68+ and CD163+) lung macrophages. Analysis of cytokine profiles in lung tissue lysates showed a hypoxia-induced upregulation of TIMP-1, CINC-1, and Fractalkine and downregulation of soluble ICAM (sICAM). The expression of Fractalkine and VEGFα, but not CINC-1, TIMP-1, and sICAM was downregulated by butyrate. In rat microvascular endothelial cells (RMVEC), butyrate (1 mM, 2 and 24 h) exhibited a protective effect against TNFα- and LPS-induced barrier disruption. Butyrate (1 mM, 24 h) also upregulated tight junctional proteins (occludin, cingulin, claudin-1) and increased the acetylation of histone H3 but not α-tubulin. These findings provide evidence of the protective effect of butyrate on hypoxic PH and suggest its potential use as a complementary treatment for PH and other cardiovascular diseases.

Cannabidiol attenuates pulmonary arterial hypertension by improving vascular smooth muscle cells mitochondrial function

Rationale: Pulmonary arterial hypertension (PAH) is a chronic disease associated with enhanced proliferation of pulmonary artery smooth muscle cells (PASMCs) and dysfunctional mitochondria, and the clinical therapeutic option for PAH is very limited. Recent studies showed that cannabidiol (CBD), a non-psychoactive constituent of cannabinoids, possessed antioxidant effect towards several cardiovascular diseases, whereas the mechanistic effect of CBD in PAH is unknown.

Methods: In this study, the effects of CBD in PAH were determined by analyzing its preventive and therapeutic actions in PAH rodent models in vivo and PASMCs' proliferation test in vitro. Additionally, CBD's roles in mitochondrial function and oxidant stress were also assessed in PASMCs.

Results: We found that CBD reversed the pathological changes observed in both Sugen-hypoxia and monocrotaline-induced PAH rodent models in a cannabinoid receptors-independent manner. Our results also demonstrated that CBD significantly inhibited the PASMCs' proliferation in PAH mice with less inflammation and reactive oxygen species levels. Moreover, CBD alleviated rodent PAH by recovering mitochondrial energy metabolism, normalizing the hypoxia-induced oxidant stress, reducing the lactate overaccumulation and abnormal glycolysis.

Conclusions: Taken together, these findings confirm an important role for CBD in PAH pathobiology.